Discovery could save wheat farmers millions

Oct 18, 2013

Epigenetic factors identified as key to preventing wheat industry losses caused by rain and high humidity.

THE global wheat industry sometimes loses as much as $1 billion a year because prolonged rainfall and high humidity contribute to grains germinating before they are fully mature, resulting in both a lower yield of wheat and grains of inferior quality.

This phenomenon, known as pre-harvest sprouting (PHS), has such important economic repercussions for farmers around the world that scientists have been working on finding a solution to the problem for at least a couple of decades.

Their focus has been on genetic factors and on the interaction between genotypes and the environment as they have tried to breed wheat that is resistant to PHS. So far, they have had little success.

Now, however, findings by a McGill University team suggest that the solution may lie not with genetics alone but, rather, with a combination of genetic and epigenetic factors.

The team, led by professor Jaswinder Singh of the department of plant science, has identified a key gene that acts as a switch to determine how a particular plant will respond to high humidity and excess rainfall by either germinating early (PHS) or not. This switch is found in a key gene, ARGONAUTE4_9, in the "RNA-dependent DNA Methylation" (RdDM) pathway.

"The complex RdDM machinery is composed of several proteins that guide the genome in response to growth, developmental and stress signals. It's a bit like the plant's brain," Singh said. "Although in the past, scientists have identified it as the pathway that regulates the way a variety of genes are expressed, until now, no one had made the link with PHS."

The McGill team made the discovery by using a variety of genomic and molecular tools to identify specific ARGONAUTE4_9 genes and then comparing the way these genes are expressed in PHS-resistant versus PHS-susceptible varieties of wheat.

"This discovery is important for other cereals like barley as well as for wheat," said Surinder Singh, a Ph.D. student and one of the authors of the study. "This means that not only should we be able to avoid the ugly bread and sticky crumbs produced by PHS wheat in the future, (but) we should also end up with better beer."

The research opens up a new area of exploration for scientists as they try to increase the yields of wheat and decrease losses due to excessively humid conditions.

The research was funded by the Natural Sciences & Engineering Research Council of Canada.